Ingot making



Patented Mar. 10, 1931 UNITED STATES PATENT} OFFICE SAMUEL B. SHELDON, OF DULUTH, MINNESOTA; FIRST AND AMERICAN NATIONAL BANK OF DULUTH EXECUTOR OF SAID SAMUEL B. SHELDON, DECEASED INGOT MAKING m5 Drawing.

This invention relates to the manufacture of steel and the like, and in another aspect it is concerned with the provision of animproved process for use in making steel billets and to a novel and improved piercing billet obtained from the practice of the process.

It is an object 0 the present-invention to provide a process which maybe racticed to diminish substantially, or to elim nate, the presence of defects in the surface of steel billets.

In the manufacture of steel billets for use in making such products as seamless tubing, rails, etc., extreme difliculty has been experienced in obtaining 7 surface imperfections. In the recent past, it was customary to expend a considerable amount of money in chippin out by hand surface defects in the billets in order to insure a perfect surface resulting in the finished type, the rail, or other product. Such a process was not satisfactory, however, because it was found that even if the chipping was carried out after first pickling the rounds that defects-would still result because of the presence in the surface of the billets of pits and such, invisible to the naked eye, which would open up in the subsequent piercing, rollin or drawing operation. It is believed that efects of this particular kind are immediately due to zones of lesser density in certain portions of the surface of the steel than in other portions thereof and that these zones are not sufficiently strong to withstand the strains and stresses that are imparted during the piercing, rolling, or. drawing operations.

The existence in the surface of the billet of zones of lesser density may be owing to a great many reasons. For example, it is believed that during the course of molding the ingot, gases exude from the poured metal and gather along the sides of the mold, forming bubbles which result in pits and blow holes being present in the molded ingot. It has been found that such imperfections may be substantially reduced by coating the interior of the mold with powdered aluminum, or an aluminum wash, which, it is believed,

a billet that is free of Application fled April 1, 1929. Serial 1T0. 851,815.

reacts in such a way as to' reduce or to eliminate the occluded'gases whereby the bubbles appear only in small amounts or are eliminated entirely.- This method of eliminating surface imperfections is good practice, and accordingly it constitutes'one of the steps in the present invention. On the other hand, in order to produce billets that will satisfactorily withstand the strains and stresses of subsequent rolling, drawing, or piercing operations it has been found desirable to o beyond the step of coatin the mold, an it is accordingly a feature of the present process to combine with the step of reducing surface porosity during the molding operation, a subsequent step which combines with the former step to such an extent that billets having billets by removing a substantial uniform V depth of material throughout the entire length thereof.

In combining these steps into a single process, it has been found that the practice of the first step decreases the time and expense of practicing the second, and that the practice of the second in turn eliminates from the billets the deleterious effects of the first, and also eliminates other imperfections not treated,

nor brought into existence, during the practice of the first step.

In another aspect an object of the invention consists in the provision as an improved article of manufacture of a piercing billet made in accordance with the invented process. Such billets are better than billets heretofore ,made and are particularly suited to piercing.

Other objects and features of the invention will appear as the description proceeds- In the practice of the improved process, an ingot mold is coated on the interior surface thereof with powdered aluminum, or a wash thereof, or a wash of any other suitable material and thereafter the mold is allowed to dry. When the mold is completely dried, molten steel is poured thereinto through the nozzle of the ladle and is allowed to solidify. During this period gases exude from the molten mass and form bubbles between the walls of the mold and the metal. It is believed, however, that the aluminum or other material on the walls of the mold combine and react with the bubbles substantially to eliminate them, whereby the formation of pits and blow holes in the surface of the ingot are substantially reduced and in many instances eliminated.

It is true, however, that the aluminum will, in localized areas, penetrate into the steel ingot causing an alloying action to take place at such areas.

After the mold has become solidified, it'is stripped from the mold and placed in soaking vats to assume a proper rolling temperature. When such a temperature has been imparted to the ingot it is sent to the rolls and rolled into a round.

Inasmuch as the molten metal in the mold contains a certain amount of slag or other impurities these bodies fioat to the top of the mold and cause the top portion of thecompleted ingot to be unfit for use. The same applies to the bottom of the ingot which is in contact with the bottom of the mold, and in view of this fact it is customary to form the ingots as long as possible in order that the waste material will be correspondingly small. Accordingly, when the ingots have been rolled they are sawed to the proper length and permitted to cool.

The next step in the process consists in passing the round through a machine which removes from the surface of the round a uniform depth of material throughout its entire length. This operation is extremely important inasmuch as the skin which is removed contains a certain amount of surface imperfections and also the aforementioned local ized alloyed areas.

Subsequently to the peeling operation any remaining porosity in the billet may be removed by chipping whereby the final product is substantially free or completely free of surface porosity.

Next the clean surfaced billets are reheated and sent to the proper machines for rolling, drawing, piercing, etc., as the case may be.

The method is of peculiar importance in makin piercing billets for seamless tubing. Such illets, especially for larger sizes of tubing, are subjected to very heavy strains in the plercing operation which tend to distort and stretch the metal, and it is particularly important that the outer surface of the billet be good and free from incipient cracks and similar defects which would lead to a rupture of the steel during the piercing operation. Billets made by my process have been found superior in this respect to those made by previous methods.

The billet produced is particularly suited to piercing, and inasmuch as such billets are complete articles of production and commerce, an important angle of the invention resides in the provision of such a billet as an article of manufacture.

Having thus described my invention what I claim as new and desire to secure by United States Letters Patent is:

1. That improvement in methods of manufacturing steel billets which comprises forming an ingot having an alloy skin, and subsequently removing the skin whereby surface imperfections are substantially eliminated from the resulting billet.

2. That improvement in methods of manufacturing steel billets which comprises forming an ingot having an aluminum alloy skin, and subsequently removing the skin whereby surface porosity in the resulting billet is substantially eliminated.

3. That improvement in methods of manufacturing steel billets which comprises coating a mold with a material suitable in diminishing the surface porosity of the molded ingot, pouring the mold, stripping the in ct from the mold, and removing the outer s 'n of the ingot to diminish still further the surface porosity of the resulting billet.

4:. That improvement in methods of manufacturing steel billets which comprises coating a mold with aluminum to diminish the surface porosity of the molded ingot, pouring ,the mold, stripping the ingot from the mold. and removing the outer skin of the ingot to diminish still further the surface porosity thereof.

That improvement in methods in manufucturing steel billets which comprises forming an ingot with an aluminum allo sln'n, and subsequently machining the bi let to remove a substantially uniform de th of material from the lengthwise surface t ereof, whereby surface porosity is substantially eliminated.

6. That improvement in methods of manufacturing steel billets which comprises coating a mold withaluminum to diminish the surface porosity of the molded ingot, pouring the'mold, stripping the ingot from the mold, and removing the outer skin of the ingot by machining to a uniform depth throughout the entire length of the ingot to diminish still further the surface porosity of the resulting billet.

7. That improvement in the method of manufacturing round steel piercing billets for the production of seamless tubing which comprises casting steel ingots with a coatin whlch diminishes their surface porosity, an

subsequently machining such ingots to av depth sufficient substantially to eliminate surface porpsity in the resulting billet.

8. That improvement in the method of manufacturing round steel piercing billets for the production of seamless tubing which comprises casting steel ingots with a coating comprising powdered aluminum which diminishes the surface porosity of the billets and subsequently machining the ingots to remove an a proximately uniform depth of material su cient substantially to eliminate surface porosity in the resulting billet.

Signed at Duluth, Minnesota, this 26th day of March, 1929.

SAMUEL B. SHELDON. 

